射频磁控溅射制备Bi2Te3热电薄膜

通过射频磁控溅射，在溅射气体为Ar，气压为1Pa，溅射功率为120W时分别在聚氨酯和玻璃基底上沉积了不同厚度的Bi2Te3薄膜。Bi2Te3薄膜主要是以（221）晶面平行于基底进行外延生长，先在基底形成大量微小晶粒，合并长大成典型的纤维状组织结构。在此条件下薄膜生长速率为26nm/min，通过控制溅射时间可沉积几纳米到几微米不同厚度的薄膜。得到的p-型半导体Bi2Te3薄膜，其电阻率随薄膜厚度的增大而减小。     

制备条件对Bi2Te3和Bi0.5Sb1.5Te3材料热电性能的影响

采用水热法制备Bi2Te3/Sb2Te3纳米粉体并热压制备块体热电材料.用X射线衍射分析产物的相结构和成分,扫描显微镜与透射电镜观察产物的形貌.测量试样从室温到700K的塞贝克系数与电导率.实验结果表明,使用水热法制备了Bi2Te3与Sb2Te3纳米粉体,经热压后部分氧化.热压温度对于块体试样热电性能影响显著.     

Bi_2Te_3柔性热电薄膜发电器件

在几种形状不同的柔性电路板上磁控溅射Bi_2Te_3薄膜,温差测试之后进行结构的优化设计。在给予一定温差条件下,测量优化设计后的柔性热电薄膜在退火前后的输出电压和电阻率,并提出了改进措施。研究表明:优化后的柔性热电薄膜相较之前有很大的改善;柔性热电薄膜输出的电压与提供的温差近似呈线性关系;在温差为200K时,输出电压为310mV,电阻率为0.792mΩ·cm;200℃/h真空退火后,输出电压增大到368mV,电阻率也同时增大,达到0.869mΩ·cm。     

放电等离子烧结制备的Bi2Te3／Sb2Te3复合材料的热电性能

研究了用低温湿化学法和水热法制备纳米级的Bi2Te3和sb挪e3颗粒，并通过透射电镜观察其微观形貌。Bi2Te3粉末的微观形貌为直径在30-50n之间的片状小颗粒，而sb2Te3颗粒的微观形貌为薄带状，直径约为70nm，长度则为从150-300nm不等，并对其晶体的形核和长大机理进行了讨论。认为，纳米小颗粒状的Bi2Te3晶体可能是通过“表面形核和侧向生长”形成的产物，而薄带状的sb2Te3晶体可能是在Te块解体形成的条带状碎屑基础上形成的。用放电等离子烧结法（spark plasma sintering）制备不同比例的Bi2Te3／Sb2Te3块状复合材料，测量并比较了其热电性能。通过改变Bi2Te3的量，可以提高复合材料的电性能。成分不同的层片间的散射，能更有效地降低块体材料的热导率。在500K的温度下，Bi2Te3和sb2Te3以摩尔比为1：1复合烧结的试样的热导率低达0．7W／（m·K）。进一步优化Bi2Te3和sb2Te3的复合比例，其热电性能可能会有进一步的提高。     

Bi2Te3热电薄膜的电化学原子层外延制备

采用电化学原子层外延法(ECALE)在Au电极上成功地制备了Bi2Te3化合物热电薄膜.通过循环伏安扫描研究Te和Bi在Au衬底上的电化学特性,使用自动沉积系统交替欠电位沉积Te、Bi原子层200个循环获得沉积物.XRD、EDX和FESEM测试结果表明循环沉积200层后得到的沉积物Bi和Te的化学计量比为2:3,且是Bi2Te3薄膜化合物,而非单质Bi和Te的简单混合;薄膜均匀、致密、平整且可重复性好,以(015)为最优取向外延生长的.     

湿化学法制备纳米Bi2Te3基热电材料的研究进展

Bi2Te3基热电材料是室温下性能最好的热电材料。传统块体Bi2Te。基热电材料的热电性能不高,而纳米Bi2Tes基热电材料可以实现电、声输运特性的协同控制,从而提高材料的热电性能。介绍了几种纳米Bi2Te3。基热电材料不同的湿化学制备方法,比较了各种方法的优缺点,并展望了其发展方向。     

块体Bi2Te3基热电材料性能优化及最新进展

在分析块体Bi2Te3基热电材料性能优化设计思路的基础上,重点探讨了成分优化、结构优化、合成优化及成型优化中提高块体Bi2Te3基热电材料性能的方法。提出了一套值得探讨的优化设计方案,展望了Bi2Te3基热电材料在温差发电和半导体制冷领域颇具潜力的应用前景。     

Bi2Te3基热电材料的研究现状及发展

热电材料是能将热能和电能直接相互转化的功能材料,它的出现为解决能源紧缺和环境污染提供了广阔的应用前景.从理论和实验两个方面对Bi2Te3基热电材料近年来国内外的研究现状及发展进行了简要介绍和评述,并指出了今后的发展方向.在理论上主要基于能带理论、半导体超晶格以及密度泛函理论去寻求影响该材料的相关因子,在实验上主要采用分子束外延、激光脉冲沉积、合金化和水热合成法等方法制备该热电材料.     

(GeTe)nBi2Te3的结构与热电性能研究

在GeTe-Bi₂Te₃赝二元系统中, (GeTe)_n(Bi₂Te₃)_m化合物往往具有较低的晶格热导率, 但其中很多组分的热电性能尚未得到系统研究。本研究通过熔融、淬火、退火结合放电等离子烧结工艺制备了一系列(GeTe)_nBi₂Te₃(n=10, 11, 12, 13, 14)单相多晶样品, 并对其相组成和热电性能进行表征和研究。掺杂Bi₂Te₃可以显著增强点缺陷声子散射, 大幅度降低材料的晶格热导率, 在723 K时, (GeTe)₁₃Bi₂Te₃样品的总热导率低至1.63 W?m ^-1?K ^-1。此外, 掺杂Bi₂Te₃和调控GeTe的相对含量, 提高了材料的载流子有效质量, 即使在较高的载流子浓度下, 样品依然保持较高的塞贝克系数和功率因子, 在723 K, (GeTe)₁₃Bi₂Te₃样品获得最大的功率因子为2.88×10 ^-3 W?m ^-1?K ^-2, 最终(GeTe)₁₃Bi₂Te₃样品在723 K获得的最大ZT值达到1.27, 较未掺杂的GeTe样品提高了16%。     

Bi2Te3基热电薄膜材料的制备方法研究

Bi2Te3基热电材料由于在微电子、光电子等高技术领域具有潜在的应用前景,从而得到了人们的广泛关注.低维Bi2Te3基热电材料由于具有特殊的量子限制效应,已成为提高热电性能的有效途径.近年来,研究者非常重视Bi2Te3基热电薄膜的制备及性能研究,并做了大量相关的研究工作,许多制备方法也相继出现,并获得了高质量的Bi2Te3基热电薄膜.     

Bi_2Te_3/炭黑复合材料的制备及热电性能

采用水热法合成Bi_2Te_3粉体,将炭黑(CB)与其掺杂制备不同比例的碲化铋/炭黑(Bi_2Te_3/CB)复合材料,研究复合材料的热电性能。同时采用TGA、SEM、XRD等分析方法表征Bi_2Te_3/CB复合材料的结构,探究微观结构与热电性能的关系。研究发现:室温下,CB的引入使Bi_2Te_3/CB复合材料的热导率大大降低(0.5957 W/(m·K)降到0.0888 W/(m·K));随着Bi_2Te_3含量的增加,复合材料的电导率、热导率均增大,Seebeck系数先增加后降低;当Bi_2Te_3含量为88.9%时,在558℃烧结10min所得的Bi_2Te_3/CB复合材料室温下热电优值ZT最大(ZT=0.21)。虽然ZT值未能达到应用价值,但是CB的添加为改善Bi_2Te_3材料的热电性能,尤其在降低材料的热导率方面,提供了新方法和新思路。     

Rational synthesis of ultrathin n-type Bi2Te3 nanowires with enhanced thermoelectric properties

A rational yet scalable solution phase method has been established, for the first time, to obtain n-type Bi(2)Te(3) ultrathin nanowires with an average diameter of 8 nm in high yield (up to 93%). Thermoelectric properties of bulk pellets fabricated by compressing the nanowire powder through spark plasma sintering have been investigated. Compared to the current commercial n-type Bi(2)Te(3)-based bulk materials, our nanowire devices exhibit an enhanced ZT of 0.96 peaked at 380 K due to a significant reduction of thermal conductivity derived from phonon scattering at the nanoscale interfaces in the bulk pellets, which corresponds to a 13% enhancement compared to that of the best n-type commercial Bi(2)Te(2.7)Se(0.3) single crystals (~0.85) and is comparable to the best reported result of n-type Bi(2)Te(2.7)Se(0.3) sample (ZT = 1.04) fabricated by the hot pressing of ball-milled powder. The uniformity and high yield of the nanowires provide a promising route to make significant contributions to the manufacture of nanotechnology-based thermoelectric power generation and solid-state cooling devices with superior performance in a reliable and a reproducible way.     

纳米结构Bi2Te3基热电材料的溶剂热合成

本文评述了近年来溶剂热合成纳米结构Bi2Te3的研究进展，重点讨论了合成过程中的化学反应和晶体生长机制，特别是Bi2Te3纳米管的合成、形成机制和组织结构特征．介绍了含纳米结构Bi2Te3的Bi2Te3基同质纳米复合结构热电材料，其热电优值ZT达到1．25，远高于基体材料，也超过目前的块状先进Bi2Te3基热电材料．     

MOCVD of Bi2Te3 and Sb2Te3 on GaAs substrates for thin-film thermoelectric applications

Metal organic chemical vapour deposition (MOCVD) has been investigated for growth of Bi2Te3 and Sb2Te3 films on (001) GaAs substrates using trimethylbismuth, triethylantimony and diisopropyltelluride as metal organic sources. The surface morphologies of Bi2Te3 and Sb2Te3 films were strongly dependent on the deposition temperatures as it varies from a step-flow growth mode to island coalescence structures depending on deposition temperature. In-plane carrier concentration and electrical Hall mobility were highly dependent on precursor ratio of VI/V and deposition temperature. By optimizing growth parameters, we could clearly observe an electrically intrinsic region of the carrier concentration over the 240 K in Bi2Te3 films. The high Seebeck coefficient (of -160 microVK(-1) for Bi2Te3 and +110 microVK(-1) for Sb2Te3 films, respectively) and good surface morphologies of these materials are promising for the fabrication of a few nm thick periodic Bi2Te3/Sb2Te3 super lattice structures for thin film thermoelectric device applications.     

Study of the strain-resistance properties of massive samples of Bi2Te3-Sb2Te3 and Bi2Te3-Bi2Se3

The coefficients of strain sensitivity of polycrystalline samples of ternary alloys based on bismuth and antimony chalcogenides were measured and the strain sensitivity of Peltier thermocouples of low height under real working conditions were evaluated.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 56, No. 1, pp. 97–99, January, 1989.     

Preparation of Bi2Te3 thermoelectric powders by applying the recycled TeO2 to wet chemical process

Extraction of TeO₂ from the byproduct solution generated during the copper smelting process and application of the extracted TeO₂ to the preparation of Bi–Te alloy thermoelectric materials were performed via a wet chemical processes. In the wet chemical process, powder purifying steps were optimized by adjusting the pH of NaOH solvent to dissolve the initially extracted Te compounds and by washing the finally extracted powders. TeO₂ powders used in preparing the Bi–Te alloy thermoelectric materials could be successfully extracted from the byproduct solution by the optimized wet chemical process. Powders synthesized by applying the commercial and the extracted TeO₂ powders to the wet chemical process showed identical crystal structures of Bi₂Te₃ and a mean particle size of ～3 μm. Thus, it is believed that the recycled TeO₂ powders will be very useful in the preparation of Bi–Te alloy thermoelectric materials.     

Effects of excess Te on the thermoelectric properties of p-type 25% Bi2Te3-75% Sb2Te3 single crystal and hot-pressed sinter

Effects of excess Te on the thermoelectric properties of p-type 25% Bi₂Te₃-75% Sb₂Te₃ single crystal and hot-pressed sinter were characterized and understood with the micro-phase diagram near the stoichiometric composition obtained by measuring the equilibrium Seebeck coefficient. Thermoelectric properties of the 25% Bi₂Te₃-75% Sb₂Te₃ single crystal were varied with the amount of excess Te, as -phase of the single crystal becomes less Te-deficient with adding more excess Te. However, thermoelectric properties of the hot-pressed sinter were not varied with the amount of excess Te, because the composition of -phase is not changed with the amount of excess Te. While a maximum figure-of-merit of 2.39 × 10^–3/K at 300 K was obtained for the 25% Bi₂Te₃-75% Sb₂Te₃ single crystal by adding 6 wt % excess Te, the hot-pressed 25% Bi₂Te₃-75% Sb₂Te₃ sinter exhibited the figure-of-merit of 2.97 × 10^–3/K regardless of the excess Te amount.     

Mechanical properties of Bi(x)Sb(2-x)Te3 nanostructured thermoelectric material

Research on thermoelectric (TE) materials has been focused on their transport properties in order to maximize their overall performance. Mechanical properties, which are crucial for system reliability, are often overlooked. The recent development of a new class of high-performance, low-dimension thermoelectric materials calls for a better understanding of their mechanical behavior to achieve the desired system reliability. In the present study we investigate the mechanical behavior of nanostructure bulk TE material p-type Bi(x)Sb(2-x)Te(3) by means of nanoindentation and 3D finite element analysis. The Young's modulus of the material was estimated by the Oliver-Pharr (OP) method and by means of numerically assisted nanoindentation analysis yielding comparable values about 40 GPa. Enhanced hardness and yield strength can be predicted for this nanostructured material. Microstructure is studied and correlation with mechanical properties is discussed.     

Radial electric field effect on thermoelectric transport properties of Bi2Te3 cylindrical nanowire coaxial structure

Radial electric field effect (REFE) on the thermoelectric figure of merit and Seebeck coefficient S are studied for a coaxial cylindrical capacitor configuration on the basis of bipolar intrinsic semiconductors. Theoretical analysis of REFE nanowire was done based on Poisson's equation in cylindrical geometry with corresponding boundary conditions. Using Newton's method the radial variation of the local Seebeck coefficient, carrier concentration and others transport characteristics are calculated for the bipolar Bi₂Te₃ nanowires neglecting size quantization. The dependence of the thermoelectric parameters on the gate voltage is studied. It is shown that the existence of the transition bipolar–monopolar semiconductor, electric field, differences in carrier masses and mobility essentially affect the thermoelectric properties. The thermoelectric figure of merit can be significantly increased by REFE.